updateJapan's network density and diversity within and beyond its shores, as well as local operators' installation of specialized civil works, helped assure the robustness of the country's telecommunication network in the aftermath of the Mar. 11 earthquake, according to an industry analyst.

However, fixed communications devices remain vulnerable to power disruption and the problem is likely to escalate as the number of networked consumer devices for fixed network grows, said David Kennedy, research director at Ovum, in a report released Wednesday.

The 9-magnitude earthquake which also triggered tsunami waves demonstrated that users were becoming more reliant on mobile communication devices, Kennedy said, noting that telecommunication network traffic grew exponentially after the tremor as customers attempted to get in touch with loved ones.

Major Japanese telcos have since restored several fixed and mobile services in the worst-hit areas, but disruptions to fixed service are still a challenge. He added that operators were likely prioritizing repair works for mobile network over fixed communication because the latter remained vulnerable to rolling power blackouts, caused by power shortages arising from the damaged nuclear plants.

KDDI had 1,500 non-functioning base stations, down from 3,800, while Softbank reduced its inoperative base stations from 3,786 to 1,157, he said. NTT DoCoMo also reported that 2,130 of its mobile base stations were still not out of service, compared to 6,720 which were inoperative immediately after the quake, he added. [Editor's note: As of 1 p.m. on Mar. 23 local time, the number of inoperable base stations dropped to 840.]

As of 1 p.m. on Mar. 23 in Japan, NTT East said it restored 90 percent of its 1,000 exchange offices damaged in the quake and recovered commercial power supply. It noted that 93 exchange offices and approximately 155 thousand circuits have yet to be restored.

The company added that a significant amount of time would be required to recover the remaining offices because damages extended beyond physical damage, and included flooding or disruption of connection to backbone transmission lines in the severely affected areas and off-limit areas surrounding the damaged nuclear power plant.

Kennedy noted that several submarine cables were damaged in the quake but service providers had been able to resolve service disruption efficiently due to Japan's robust network. And while there were disruptions to international communications, as a result of reported cable breaks, connectivity was "surprisingly robust", especially when compared to the 2006 Taiwan earthquake.

Kennedy explained: "The density and diversity of the networks within and out of Japan creates many redundancy paths, which prevented major service disruption outside of the worst affected areas.

"[In addition,] operators had installed specialized civil works which can cope with earthquakes, having learned many lessons from the Kobe earthquake of 1995. Flexible underground conduits between street infrastructure and buildings, sliding joints for ducts to relieve axial forces, and flexible joints in manhole and other access tunnels have become commonplace in new installations since 1995," he said.

Although repair work is progressing steadily, Ovum expects new problems to surface in the coming weeks as damaged infrastructure--on land and in sea--fails.

Kenney noted that vibrations from the quake can cause soil to liquefy, damaging pits, ducts and cables. This would allow water to enter and damage the undersea cable systems, leading to further network failures weeks after the earthquake, he added.